The present invention relates to systems for vehicles. More particularly, the invention relates to a system for a vehicle, comprising:
a vehicle seat which comprises a seat part and a backrest defining an accommodating space intended to accommodate an occupant,
a measuring device of the electromagnetic field type comprising at least one pair of electrodes arranged in the seat part, to generate an electromagnetic field in said accommodating space and to measure at least one value associated with an electromagnetic characteristic of propagation of said electromagnetic field in the accommodating space,
at least one actuator device (for example an airbag, or other) having several modes of operation,
and an operating device designed to cause the actuator device to operate selectively according to one of its modes of operation depending on said value measured by the measuring device.
It will be noted that the expression xe2x80x9celectromagnetic fieldxe2x80x9d as used here refers to a static or variable electric and/or magnetic field. The expression xe2x80x9celectromagnetic characteristic of propagation of the fieldxe2x80x9d, as used here, in particular encompasses electric permittivity.
Document WO-A-00/25 098 describes one example of such a system, in which the actuator device is an airbag and the measuring device is designed to detect the position of the occupant of the seat.
However, although it is particularly advantageous to provide the airbag operating device with information about the position of the occupant of the seat, it is often necessary to provide this operating device with information regarding the mass of the occupant. In this case, recourse is generally had to other sensors such as strain gauges arranged under the seat part of the seat or in this seat part, which makes the seat more complicated and more expensive.
It is a particular object of the present invention to alleviate these drawbacks.
To this end, according to the invention, a safety device of the kind in question is characterized in that said operating device has a memory in which is stored a mass parameter representing the mass of the occupant of the seat, said operating device being designed to choose the mode of operation of the actuator device according to said mass parameter, and in that the system comprises at least one central electronic unit designed to determine said mass parameter on the basis of said value measured by the measuring device and to transmit said mass parameter to said memory of the operating device.
By virtue of these provisions, the use of additional sensors such as strain gauges can be avoided, this making it possible to simplify the vehicle seat and reduce its cost price. It will be noted that this advantage exists even when the actuator device does not use position information: this is because the information then possibly makes it possible for at least part of the measuring device to be standardized for systems using only the measurement of the weight of the user and those using both the detection of the position and the measurement of the weight of the user.
In some preferred embodiments of the invention, recourse may possibly also be had to one and/or other of the following arrangements:
the actuator device is an airbag designed to protect the occupant of the seat in the event of an accident, and the operating device is designed to inflate the airbag in the event of an accident;
the memory of the device for controlling the airbag further comprises at least one position parameter representing a position of the occupant in the seat, this operating device being designed to choose the mode of operation of the airbag according to said position parameter, and said central electronic unit being designed to determine said position parameter on the basis of said value measured by the measuring device and to transmit said position parameter to said memory;
said central electronic unit belongs to the measuring device;
the measuring device comprises at least two pairs of electrodes arranged in the seat part of the seat;
the measuring device further comprises at least one pair of electrodes arranged in the backrest of the seat;
each electrode of the measuring device is in the form of a sheathed flexible conducting wire of a length of between 10 and 40 cm, the two electrodes of each pair of electrodes being separated from one another by a distance of between 2 and 10 cm;
the measuring device is designed to generate an electric field in said accommodating space and to measure at least one value associated with a characteristic of propagation of the electric field in said accommodating space;
said characteristic of propagation of the electric field in the accommodating space is the electric permittivity;
the measuring device is designed to generate an electric field that is continuous in periods;
the measuring device is designed to generate an electric field which is continuously variable;
the mass parameter is a mass category.